Size-tunable optical properties and the ability to process thin films using scalable, cost-efficient printing techniques make colloidal nanocrystals (NCs) an attractive candidate for solar cells, light-emitting devices, transistors, photodetectors, and batteries. Colloidal synthesis of conventional NCs using metal-based compound semiconductors (groups III-V, II-VI, and IV-VI) yields non-polar or polar ligands bound to the NC surface through labile Lewis acid-base or ionic surface bonds. Progress in NC materials, and electronics that utilize them, may be advanced by developing methods that enable the manipulation of NC surfaces through displacement of labile native insulating ligands.
Whereas surface manipulation has launched metal-based NCs to the forefront of NC-based optoelectronics research, similar strategies using non-toxic and earth-abundant group IV (e.g. Si, Ge) NCs have largely been unsuccessful owing to the covalent bonds that dominate these nanostructures. Though functionalization of group IV NCs with covalent Si—C or Ge—C bonds (primarily through reaction with an alkene via hydrosilylation or hydrogermylation) can minimize the impacts of oxidation as well as enhance photoluminescence, these group IV-C bonds are kinetically inert and typically do not undergo exchange.
Some advances have been made towards functionalizing group IV NCs to provide ligand exchange surface reactions. However, most studies have resulted in irreversible, incomplete, and/or only quasi-reversible ligand exchange reactions. Thus, there remains a need for methods that provide reversible and complete ligand exchange chemistry to occur on the surfaces of group IV NCs.